Environmental Impact Assessment of Road Traffic in Taiz City. 3/H4303425… · ·...

Dr. Fareed M. A. Karim Int. Journal of Engineering Research and Applications www.ijera.com

ISSN : 2248-9622, Vol. 4, Issue 3( Version 3), March 2014, pp.42-55

www.ijera.com 42 | P a g e

Environmental Impact Assessment of Road Traffic in Taiz City.

Dr. Fareed M. A. Karim Faculty of Engineering, University of Aden, YEMEN.

Abstract In this study an attempt was made to estimate and predict the pollution emission by road traffic in Taiz city

(Yemen). Mobile 6.2 software designed by EPA in the united states was used for the estimation of the pollutions

such as CO, THC, NOx , SO2 and PM. Hourly classified vehicle count was carried out in the city network in

year 2010, and forecasted for the year 2014, 2020 and 2025. The metrological data, vehicle fleet characteristics

and fuel specifications of Taiz city were fed in the software. The pollution emission for the year 2014, 2020 and

2025 were obtained. Different scenarios such as clean air act and traffic management plan in the city were

investigated in order to reduce the pollution emissions.

Keywords: Traffic Air Pollution, Urban traffic Pollution, Mobile 6.

I. Introduction Taiz is one of the 22 governorates of

Yemen. It extends over 14,194 sq.km and accounts

for 2.69 % of Yemen’s geographical area and

contained a population of 2,805,000 (2010)

accounting for 12.1 % of the country’s population.

Taiz governorate has the biggest population size

among all the governorates. The urban share is

22.8%.

Taiz city is the capital of Taiz governorate.

It is a historical city of long vintage and hosts a

number of heritage monuments and buildings

attracting a large number of tourists. The city is built

along hilly terrain of steep slopes and provides a

great example of human ingenuity in city

building. Located in the interior highlands at

altitudes ranging between 1,100 m and 1,600 m

above sea level. Its center became jammed due to its

traditional narrow streets and the lack of proper

traffic and parking management system. Figure (1)

shows the map of the Republic of Yemen, while

figure (2) shows Taiz metropolitan Region and figure

(3) shows the Taiz city road network.

Figure (1): Republic of Yemen.

RESEARCH ARTICLE OPEN ACCESS




Figure (2 ): Taiz Metropolitan Region.

Figure (3): Taiz city Road Network.




II. Environmental Characteristics Due to the absence of heavy industries in

Taiz, and coupled with heavy rainfall and

mountainous terrain resulting high wind speeds.

The traffic is major source of pollution in the city,

deterioration of environment might occur due to

rapid increase in private vehicles

III. Increase in Registered Vehicles The registered vehicles in Taiz have

grown at a rapid average annual growth rate of

16.5% since 1996 and are expected to grow at the

same rate. Cheap availability of old vehicles from

developed countries also has resulted in increase in

the vehicle numbers. The influence of development

of neighboring countries and some possible oil

exploration in future may cause a rapid surge in

Yemen economy, which will increase vehicle on

roads. If necessary steps are not taken in terms of

curbing the private vehicles, in future further

environmental deterioration may happen. Figure

(2) shows the growth of vehicles in Taiz.

Figure (4): Growth of vehicles in Taiz.

IV. Vehicle Technology Predominant share of vehicles on roads are

of modern technology. However, two wheelers, taxis

and commercial vehicles are still based on old

technology. Two wheelers in particular have

conventional two stroke engine and are a major cause

of vehicular air pollution and effect is enhanced due

to presence of hilly terrain.

The prime mode of public transport in Taiz

for intra city travel is medium size buses and vans

popularly known as Dhabbabs having seating

capacity of 9, 13 and 26. 13 seater Dhabbas are

more in number as compared to others. These

vehicles Dhabbabs are old diesel based vehicles with

high fuel consumption. The composition of Dhabbabs

is maximum (30%) in traffic and perform maximum

trips in a day by any mode. Diesel as fuel with high

sulphur content and low propulsion on hilly terrains

cause increase in exhausts which intern cause

increase in air pollution.

V. Age of Vehicles Predominant share of vehicles on roads are

of modern technology. However, two wheelers,

taxis and commercial vehicles are still based on old

technology. Two wheelers in particular have

conventional two stroke engine and are a major cause

of vehicular air pollution and effect is enhanced

due to presence of hilly terrain.

44% of Dhabbabs were in age band of 10-15

years and 48% are above 15 years of age. This

particular share of vehicles has been over utilized in

terms of life span. Similarly other vehicles like

Peugeot taxis and other intra city taxis constitute

more 17% of traffic and have a very high trip rate.

These all vehicles are very old and run on

conventional technology and are major source of air

pollution. There is a need to introduce new

technology based on alternative fuels for public

transport and restricting the use of over aged vehicles

particularly in urban areas.

VI. Air Quality model In this study Mobile6 model used to

estimate and predict the emission from vehicles

movement in Taiz city. MOBILE6 was designed by

the U.S. Environmental Protection Agency (EPA) to

address a wide variety of air pollution modeling

needs. Written in Fortran and compiled for use in the

desktop computer environment, the model calculates

emission rates under various conditions affecting in-

use emission levels (e.g., ambient temperatures,

average traffic speeds) as specified by the modeler.

MOBILE models have been used by EPA to evaluate

highway mobile source control strategies; by states

and local and regional planning agencies to develop

emission inventories and control strategies for State

Implementation Plans under the Clean Air Act; by




metropolitan planning organizations and state

transportation departments for transportation

planning and conformity analysis; by academic and

industry investigators conducting research; and in

developing environmental impact statements.

The model predicts emissions of hydro

carbons, carbon mono oxide, oxides of nitrogen,

particulate matter and sulfur dioxide in gram per

vehicle-mile for different types of vehicles. Vehicles

types include light duty gasoline-powered vehicles,

light duty gasoline-powered trucks, heavy-duty

gasoline-powered trucks, light-duty diesel -powered

vehicles, heavy-duty diesel-powered vehicles, and

motorcycles.

The mathematical form of the models is

basic emissions factor multiplied by a set of

correction factors related to environmental and

operating characteristics. Correction factors account

for variations in ambient temperature, fuel volatility

level, air conditioner use, loading and trailer towing,

and vehicular operating mode, speed, age, and

mileage accumulation. Total daily or annual

emissions may be predicted by multiplying the

corrected emissions factors by the total vehicle-miles

of travel for particular vehicle types and then

summing over all vehicle types.

Basic emissions rates and correction factors

are determined from the Federal Test Procedure

(FTP).

The model assumes that vehicles from the

previous 20 model years are operating during any

given year. They contain build-in estimates of he

mileage accumulation of each model year and the

distribution of model years in the fleet in any given

year. Emissions factors are assumed to increase with

age because of mechanical deterioration with

increase mileage. It is also assumed that for any

given calendar year, vehicle of any particular model

year accrue mileage, operate, and are subject to

environmental conditions similar to all other vehicles

of that model year; consequently, the model are not

sensitive to the composition of the fleet in terms of

make of vehicles.

VII. Modeling Traffic Air Pollution in Taiz

City Mobile6 software was used to estimate and

predict air pollution in Taiz city. In order Mobile6

predict correctly the emission rate by traffic, the

following input parameters have been modified in the

software:

a) Metrological data:

Min/Max Temperature

Absolute Humidity

Altitude

b) Vehicle Fleet Characteristics:

Vehicle Mile Traveled Fractions

Distribution of Vehicle Registration (Age)

Average Speed

Diesel Fractions

c) Fuel Specifications:

Gasoline Sulfur Content

Diesel Sulfur Content

Fuel Reid Vapor Pressure (RVP)

VIII. Scenarios for Modeling Traffic Air

Pollution

The Yemeni ambient air quality norms are

similar to that of adopted by United States, however,

the apart from ambient air quality standards United

States has adopted other measures like emission

norms for vehicles to curb pollution.

The Yemeni warrants for air quality no

where mentions the vehicle emission norms for

different modes. The norms for vehicle emission can

play a very important role in curbing vehicular

pollution as these norms are considered while

manufacturing vehicles. This warrants can make

technology change in vehicles and there by reducing

pollution.

Yemeni Environment protection legislation

requires amendment to include emission norms for all

vehicles and periodic pollution checks e.g. 1990

Clean Air Act amendments, Tier1, Tier2 etc...

Standards adopted by the United States EPA or

EURO 1-4 standards adopted by European Union.

Two scenarios were considered for

modeling traffic air pollution in Taiz city, viz. do

nothing scenario and alternative scenarios.

Do Nothing Scenario:

At present there are no laws or regulations in

Taiz city which prevent vehicle owners to control the

vehicular emission rate. Moreover, as mentioned

earlier, considerable amount of vehicles have old

technology and are in the age band of 10-15 years,

and many of the imported vehicles are used (old)

vehicles from developed countries. In addition, the

fuel used in the city has high percentage of sulfur

(gasoline 0.1% and diesel 0.348% by mass).

To model the above mentioned short coming

in transportation system in Taiz city, we have to

disable the 1990 Clean Air Act Amendments

requirements (CAA) in Mobile6.

Vehicular emission in Taiz city for the years

2014, 2020 and 2025 were modeled using do nothing

scenario. Table (1) shows area wise daily emission in

tons of Total Hydro Carbon, Carbon mono oxides,

Nitrogen oxides, Particulate matter and Sulfur

dioxides in Taiz in different years (do nothing

scenario).




Table (1): Area wise daily emission of pollutants in tons in different years, (do nothing) scenario.

Year Pollutants Area

Central (CBD) Mid (suburb) Outer

Cordon

Total

2014

THC 3.998 2.600 9.673 16.271

CO 30.698 19.942 69.172 119.811

NOx 3.519 2.513 15.010 21.042

PM 0.141 0.095 0.538 0.774

SO2 1.074 0.725 4.058 5.857

2020

THC 4.841 3.148 11.712 19.701

CO 37.169 24.145 83.754 145.069

NOx 4.261 3.043 18.174 25.478

PM 0.170 0.115 0.651 0.937

SO2 1.300 0.878 4.913 7.091

2025

THC 5.695 3.702 13.776 23.173

CO 43.721 28.401 98.516 170.638

NOx 5.012 3.580 21.377 29.969

PM 0.200 0.136 0.766 1.102

SO2 1.530 1.033 5.779 8.341

It is clear from Table (1) that the daily emission of

Total Hydro Carbon is 16.271 ton, 119.811 tons of

Carbon mono oxides, 21.042 tons of Nitrogen

oxides, 0.774 ton of Particulate matter and 5.857

tons of Sulfur dioxides in Taiz on a typical summer

day in year 2014. Figure (5) shows the daily

emission in tons of Total Hydro Carbon, Carbon

mono oxides, Nitrogen oxides, Particulate matter

and Sulfur dioxides in the central area for the years

2014, 2020 and 2025.




Figure (6) shows the daily emission in tons of Total

Hydro Carbon, Carbon mono oxides, Nitrogen

oxides, Particulate matter and Sulfur dioxides in

the mid area for the years 2014, 2020 and 2025.

Figure (7) shows the daily emission in tons of Total

Hydro Carbon, Carbon mono oxides, Nitrogen

oxides, Particulate matter and Sulfur dioxides in

the outer area for the years 2014, 2020 and 2025.

0

5

10

15

20

25

30

35

40

45

2014 2020 2025

Ton

s

Year

Fig. (5): Daily Emission of Pollutants in Cental Area

THC CO NOX PM SO2

0

5

10

15

20

25

30

2014 2020 2025

Ton

s

Year

Fig. (6): Daily Emission of Pollutants in Mid Area

THC CO NOX PM SO2

0

5

10

15

20

25

30

2014 2020 2025

Ton

s

Year

Fig. (7): Daily Emission of Pollutants in Outer Area

THC CO NOX PM SO2




Figure (8) shows the daily emission of different

traffic pollutants in whole Taiz for the years 2014,

2020and 2025.

These comparatively low values of traffic

emissions of various pollutants in Taiz city as

shown in Table (1), especially in central area

coupled with heavy rainfall and mountainous

terrain resulting high wind speeds which will lead

to quick dispersion of the above mentioned

pollutants.

IX. Dispersion of Air Pollutants: Pollutants emitted into the atmosphere are

mixed thoroughly with the surrounding air and

diluted by atmospheric dispersion. This dispersion is

primarily due to turbulent diffusion and bulk air flow.

In this study the Gaussian plume model was used to

predict the concentration of pollutants downwind of a

line source situated at ground level.

For infinite line source such as heavy traffic

along a long stretch of road, the ground-level

downwind concentration of pollutants is given by:

Where,

q= Q/l = source strength per unit distance (gram/ m.

sec)

u = wind speed m/sec

σ z = dispersion coefficient

The above equation was used to predict the

dispersion of traffic pollutants in the atmosphere and

to find out the concentration of pollutant in the

atmosphere in micro gram per cubic meter.

The analysis revealed that the concentration

of pollutants in the atmosphere due to traffic

movement Taiz city for the base year as well as

future years till 2025 will not exceeded the Yemeni

ambient air standards provided that there will be no

other sources of pollution such as heavy industries

etc..

However, it is advisable to think about adopting

higher emission norms such as 1990 clean air act of

the united states or European emission standards

Euro I, because in country like Yemen, adopting new

norms, training staffs and importing necessary

equipments will take years. So, if a decision taken to

adopt higher norms, may be after 5 or 10 years we

will be able to correctly implement that norm.

Alternative Scenarios:

1- Clean Air Act :

The first step to improve the traffic air

quality emission in Taiz city for the future years will

be to adopt emission norms for vehicles similar to

1990 Clean Air Act (CAA) used in the united states

(or its European counter part Euro I), then higher

norms may be thought about.

In this study, alternative analysis was carried

out using the 1990 Clean Air Act amendment. The

input to Mobile6 software was modified to take into

consideration the 1990 Clean Air Act (CAA), as well

as improved fuel specifications (sulfur 0.05 % by

mass).

0

20

40

60

80

100

120

2014 2020 2025

Ton

s

Year

Fig. (8): Daily Total Emission of Polutants in Taiz

THC CO NOX PM SO2




Vehicular emission for Taiz city for the

years 2014 and 2020 and 2025 were modeled using

alternative scenario (Clean Air Act). Table (2) shows

area wise daily emission in tons of Total hydro

carbon, Carbon mono oxide, Nitrogen oxides,

particulate matter and Sulfur dioxides.

Table (2): Area wise daily emission of pollutants in tons in different years, (Clean Air Act) scenario.

It is clear from Table (2) that the daily

emission of Total Hydro Carbon is 9.266 ton,

72.193 tons of Carbon mono oxides, 19.419 tons of

Nitrogen oxides, 0.488 ton of Particulate matter

and 0.130 tons of Sulfur dioxides in Taiz on a

typical summer day in year 2014. Figure (9) shows

the daily emission in tons of Total Hydro Carbon in

Taiz for both the scenarios, it is clear that clean air

act has considerable impact on reduction of THC

for the years 2014, 2020 and 2025.

0

5

10

15

2014 2020 2025

Ton

s

Year

Fig. (9): Daily THC Emission For Two Scnarios

DO NOTHING CLEAN AIR ACT




Figure (10) shows the daily emission in tons of

Carbon mono oxide in Taiz for both the scenarios,

it is obvious that clean air act has considerable

impact on reduction of CO for the years 2014, 2020

and 2025.


Nitrogen oxides in Taiz for both the scenarios, it is

clear that clean air act has considerable impact on

reduction of NOx for the years 2014, 2020 and

2025.

0

20

40

60

80

100

120

2014 2020 2025

Ton

s

Year

Fig. (10): Daily CO Emission For The Two Scenarios


0

5

10

15

2014 2020 2025

Ton

s

Year

Fig. (11): Daily Nox Emission For The Two Scenarios






particulate matter in Taiz for both the scenarios, it

is clear that clean air act has considerable impact

on reduction of PM for the years 2014, 2020 and

2025.


sulfur dioxides in Taiz for both the scenarios, it is

clear that clean air act has huge impact on

reduction of SO2 for the years 2014, 2020 and

2025, the main reason due to the assumption of

using clean fuel with less percentage of sulfur.

2- Traffic Improvement in Central Area:

To decongest the central area of Taiz city, a

traffic management plan was suggested by changing

two way traffic to one way in some routes. The

environmental impact of this improvement in

considered in this section. The air pollution due to

traffic at central area was compared for different

scenarios. Four scenarios were compared viz. do

nothing scenario at the central area (DN), do nothing

with traffic management plan at central area

(DNTMP) ,Clean Air Act (CAA) at the central area,

and traffic management with clean air act

(CAATMP).

0

0.1

0.2

0.3

0.4

0.5

0.6

2014 2020 2025

Ton

s

Year

Fig. (12): DailyPM Emission For The Two Scenarios


0

1

2

3

4

5

2014 2020 2025

Ton

s

Year

Fig. (13): Daily SO2 Emission For The Two Scenarios





Figures (14), (15), (16) , (17) and (18)

show the daily emission index of total hydro

carbon, carbon mono oxide, nitrogen oxides,

particulate matter, and sulfur dioxide respectively

for different scenarios.

It is clear from figure (14) that on any

typical summer day in 2014, the THC emissions

will be reduced by 21.7% if a traffic management

plan (DNTMP) is adopted at the central area, in the

same year the emission of THC will be reduced by

36.9% if clean air act (CAA) is implemented at the

central area, similarly, the emission of THC will be

reduced by 50.3% if CAA norms implemented

along with traffic management plan (CAATMP) in

2014.

Figure (15) indicates that on any typical summer

day in 2014, the CO emissions will be reduced by

22.2% if a traffic management plan (DNTMP) is

adopted at the central area, in the same year the

emission of CO will be reduced by 32.2% if clean

air act (CAA) is implemented at the central area,

similarly, the emission of CO will be reduced by

47.4% if CAA norms implemented along with

traffic management plan (CAATMP) in 2014.

0

0.5

1

1.5

2

2014 2020 2025

Emis

sio

n In

de

x

Year

Fig. (14): Daily THC Emission Index For Different Traffic Management Plans at Central Area

DN DNTMP CAA CAATMP

0

0.5

1

1.5

2

2014 2020 2025

Emis

sio

n In

de

x

Year

Fig. (15): Dail CO Emission Index For Different Traffic Management Plans at Central Area

DN DNTMP CAA CAATMP




Figure (16) reveals that on any typical summer day

in 2014, the NOx emissions will be reduced by

20.6% if a traffic management plan (DNTMP) is

adopted at the central area, in the same year the

emission of NOx will be reduced by 45% if clean

air act (CAA) is implemented at the central area,

similarly, the emission of NOx will be reduced by

56.2% if CAA norms implemented along with

traffic management plan (CAATMP) in 2014.

It is clear from figure (17) that on any typical

summer day in 2014, the PM emissions will be

reduced by 19.5% if a traffic management plan

(DNTMP) is adopted at the central area, in the

same year the emission of PM will be reduced by


central area, similarly, the emission of PM will be



2014.

Figure (18) indicates that on any typical

summer day in 2014, the SO2 emissions will be

reduced by 19.2% if a traffic management plan

(DNTMP) is adopted at the central area, in the

same year the emission of SO2 will be reduced by


0

0.5

1

1.5

2

2014 2020 2025

Emis

sio

n In

de

x

Year

Fig. (16): Daily Nox Emission Index For Different Traffic Management Plans at Central Area

DN DNTMP CAA CAATMP

0

0.5

1

1.5

2

2014 2020 2025

Emis

sio

n In

de

x

Fig. (17): Daily PM Emission Index For Different Traffic Management plans at Central Area

DN DNTMP CAA CAATMP




central area, similarly, the emission of SO2 will be



2014. It is obvious from figure (18) that using clean

fuel with 0.05 percent sulfur by mass has reduced

the emission of sulfur dioxide to great extend.

It is clear from figures (14), (15), (16),

(17) and (18) that the traffic improvement plan in

the central area has significant impact on reduction

the traffic air pollution in the central area.

X. Legislation/ Warrants for

Environment Yemen has developed a number of legal

instruments at various levels of government directly

or indirectly concerned with environment protection.

It is party to a number of international conventions,

agreements and treats that have environmental

implications. Table 3 presents the ambient air quality

standards and their comparison with standards given

by various other organizations.

Table (3): Ambient Air quality Norms

Parameter

(1)

Country or Organization

Averaging Period USA(1) WHO(2) World

Bank(3)

Japan(4) Yemen(5)

SO2

Annual 0.06 - 1.00 0.26 0.06

24-Hour

Maximum

0.365 0.90 0.50 0.11 -

24-Hour Average - - 1.00 - 0.15

1-Hour Average - 0.35 0.19 - 0.35

NO2

Annual 0.10 - 0.10 - -

24-Hour

Maximum

- - - 0.08 -

24-Hour Average - - 0.50 - 0.15

1-Hour Average - 0.19-0.32 - - 0.4

O3 1 Hour Maximum 0.235 - - 0.06 ppm 0.06 ppm

Particulates

Annual 0.065-

0.075

0.60-0.90 0.50 -

24-Hour

Maximum

0.15-0.26 - - 0.20 0.07

24-Hour Average - 0.15-0.23 - 0.10 -

1-Hour Average - - 0.20 -

0

0.5

1

1.5

2

2014 2020 2025

Emis

sio

n In

de

x

Year

Fig. (18): Daily SO2 Emission Index For Different Traffic Management Plans at Central Area

DN DNTMP CAA CAATMP




Sources:

1- USA Standards are federal Standards as reported

by the California Air Resources Board 9 January

2003.

2- World Health Organization- Standards as cited

by various websites.

3- World Bank websites, including World Bank,

Environmental Department, Initial Draft of

Industrial Pollution and Abutment Handbook,

January 1995.

4- Environmental Quality in Japan, Ministry of

Environment, Government of Japan, current

website (www.env.go.jp).

5- Implementation list of the Environmental

Protection Law, Yemen, 2005.

XI. Conclusions The following conclusions can be drawn

from this Study:

• The environmental impact study for Taiz city for

the years 2014, 2020 and 2025 were carried out

in this study.

• The Taiz fleet generates 119.8 tons of carbon

mono oxide (CO), 16.271 tons of total hydro

carbon (THC), 21.042 tons of nitrogen oxides

(NOx), 0.774 ton of particulate mater (PM) and

5.872 tons of sulfur dioxide (SO2) on a typical

summer day in 2014 (do nothing scenario).

• If Taiz city adopted higher emission norms e.g.

similar to the 1990 clean air act (CAA) of the

united states, then daily emission of Taiz city

will be reduced to 72.193 tons of (CO), 9.266

tons of (THC), 19.416 tons of (NOx), 0.488 ton

of (PM) and 0.13 ton of (SO2) on a typical

summer day in 2014.

• On any typical summer day in 2014, the CO

emissions will be reduced by 22.2% if a traffic

management plan (DNTMP) is adopted at the

central area, in the same year the emission of CO

will be reduced by 32.2% if clean air act (CAA)

is implemented at the central area, similarly, the

emission of CO will be reduced by 47.4% if

CAA norms implemented along with traffic

management plan (CAATMP) in 2014.

• Similarly, the traffic management plan at the

central area has considerable effect on the

reduction of daily emission of THC, NOx, PM

and SO2.

• Alternative fuel technologies for public transport

can be introduced in order to reduce the

emissions. Yemen having rich petroleum

resources, following fuels may be considered for

public transport.

o Standard diesel

o Ultra Low Sulfur Diesel (ULSD)

o Bio-diesel (mix of bio-mass like oil

from Jatropha plants with diesel)

o Natural gas (compressed or liquefied)

o Liquefied Petroleum Gas (LPG)

o Di-methyl Ether (DME)

• Yemeni Environment protection legislation

requires amendment to include emission norms

for all vehicles and periodic pollution checks e.g.

United States clean air act, Tier 1, Tier 2 etc... Or

EURO 1-4 standards adopted by EU.

References

[1] Central Statistical Organization (2010),

Statistical Year Book, Sana'a, Republic of

Yemen: Ministry of Planning and

International Cooperation.

[2] Consulting Engineering Services (India) Pvt

Ltd, New Delhi, (2009), Traffic

Management Master Plan for Taiz & Design

of Priority Traffic Improvements.

[3] Environmental Protection Agency, (2003),

User's guide to Mobile 6.1 and Mobile 6.2.

[4] World Bank websites, including World

Bank, Environmental Department, Initial

Draft of Industrial Pollution and Abutment

Handbook, January 1995.

[5] Environmental Quality in Japan, Ministry of

Environment, Government of Japan, current

website (www.env.go.jp).

[6] World Health Organization- Standards as

cited by various websites.

[7] Implementation list of the Environmental

Protection Law, Yemen, 2005.

[8] Krishna, K.M., Air Pollution and Control

(1999), India.

[9] EPA Standards Reference Guide (2012) ,

EPA's Office of Transportation and Air

Quality (OTAQ),

http://www.epa.gov/otaq/standards/

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